Yup. When I sold my old R1, some dude called on the ad, saying he was a truck driver, but that he'd be in Detroit in a couple days, and asked if he could come look at it, and mumbled test ride it..lmfao..I said "you come here with a certified check, buy it, and you've got 10 minutes to get your money back if you don't like it and haven't crashed it"..he hung up. 10 minutes later, another dude called about my ad, and said he was selling an R1 also, but some dude claiming to be a trucker came (told the exact same story) and "test rode" it and never came back, so he was calling everybody else that was selling the same bike and warning them. I laughed real hard and said I was sorry about his luck, and how I wished he'd called 15 minutes earlier so we could set the guy up. The "trucker" had met him at a gas station and pointed to a truck in the parking lot and said that was what he drove up in, and he'd be back in a couple minutes from the test drive. Obviously, the truck wasn't his.

I can't verify this, but I've heard that in some cases the insurance companies have refused to pay, since the vehicle owner "gave the keys" to the thief.